System and method for capturing co 2

Abstract

Disclosed are processes of removing CO2 from a CO2-containing gas stream and CO2 capture systems.

Description

71CCS-510954- WO-2_BHI0566PCTSYSTEM AND METHOD FOR CAPTURING CO2CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Italian Application No. 102024000026439, filed on November 25, 2024, which is incorporated herein by reference in its entirety.BACKGROUND

[0002] Carbon dioxide is a primary driver of global climate change; therefore, it is critical to reduce its emissions. Several processes use aqueous ammonia-based solvents to capture CO2 from gaseous streams. A mixed salt process (MSP) uses an aqueous solution of potassium carbonate and ammonium carbonate as solvent to generate a concentrated CO2 stream by absorbing and desorbing CO2 in a cyclic process using said solution as solvent. The current state of the art for ammonia-based solvent CO2 capture processes, such as the MSP process, can benefit from an energy efficient process and system for CO2 capture.SUMMARY

[0003] In an embodiment, a process of removing CO2 from a CO2-containing gas stream, the process comprises: contacting, in a first absorber section, a CO2-containing gas stream with a solvent mixture to generate a partially cleaned gas stream; contacting, in a second absorber section, the partially cleaned gas stream with a CO2-lean solvent to generate a further cleaned gas stream that contains ammonia and a CO2-partially-enriched solvent; dividing the CO2-partially-enriched solvent into a first portion and a second portion; removing the first portion of the CO2-partially-enriched solvent from the second absorber section; cooling the removed CO2-partially-enriched solvent; contacting, in a third absorber section, the cooled CO2-partially-enriched solvent with the further cleaned gas stream that contains ammonia to generate a treated gas stream and a solvent containing a recovered ammonia; and combining the solvent containing the recovered ammonia removed from the third absorber section with the second portion of the CO2-partially-enriched solvent, forming the solvent mixture used in the first absorber section; and one of A) or B): A) removing a CO2-semi-enriched solvent from a lower portion of the first absorber section and, after cooling, recirculating it to a fourth absorber section; or B) removing a CO2-semi-enriched solvent from a lower portion of the first absorber section and circulating it to a CO2-semi-rich sump to mix with a portion of a CO2- enriched solvent, and removing a mixed CO2-semi-enriched solvent from the CO2-semi-rich sump and, after cooling, recirculating it to a fourth absorber section; wherein the fourth71CCS-510954- WO-2_BHI0566PCT absorber section, the first absorber section, the second absorber section, and the third absorber section are arranged sequentially in an absorber in a direction from a gas inlet to a gas outlet.

[0004] In another embodiment, a CO2 capture system comprises: an absorber vessel comprising a first absorber section, a second absorber section, and a third absorber section, the second absorber section comprising a second gas-liquid contacting device and a second liquid collector for collecting a CCh-partially-enriched solvent which is a lean solvent that has passed through the second gas-liquid contacting device; a gas inlet for introducing a CCh-containing gas stream into the absorber vessel; a gas outlet for removing a treated gas stream from the absorber vessel; a liquid inlet for introducing the CCh-lean solvent into the second absorber section; a liquid outlet for removing a CCh-enriched solvent from the first absorber section; a first liquid delivery path for delivering an ammonia mitigation solvent, which is a first portion of the CCh-partially-enriched solvent collected on the second liquid collector, to the third absorber section; a cooling means for cooling the ammonia mitigation solvent before the ammonia mitigation solvent is delivered to the third absorber section; and a second liquid delivery path for delivering a solvent containing a recovered ammonia drawn from the third absorber section to the second liquid collector in the second absorber section so that the solvent with the recovered ammonia mixes with a second portion of the CXb-parlial ly-enriched solvent; and one of A) or B): A) further comprising a fourth absorber section comprising a fourth gasliquid contacting device and a fourth liquid distributor, and further comprising a liquid delivery path for delivering a CCh-semi-enriched solvent drawn from the first absorber section to the fourth liquid distributor; or B) further comprising a fourth absorber section comprising a fourth gas-liquid contacting device and a fourth liquid distributor; further comprising a liquid delivery path for delivering a CCh-semi-enriched solvent collected at a first liquid collector of the first absorber section to a CCh-semi-rich sump to mix with a portion of a CCh-enriched solvent drawn from a CCh-rich sump; and a liquid delivery path for delivering a mixed CCh-semi- enriched solvent drawn from the CCh-semi-rich sump to the fourth liquid distributor; wherein the fourth absorber section, the first absorber section, the second absorber section, and the third absorber section are arranged sequentially in the absorber in a direction from the gas inlet to the gas outlet.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

[0006] FIG. 1 is a simplified scheme illustrating a system and a process for removing71CCS-510954- WO-2_BHI0566PCTC02from a CCh-containing gas stream;

[0007] FIG. 2 is a simplified scheme illustrating the base concept of liquid mass flow (M) during a process of removing CO2from a CCh-conlai n i ng gas stream according to FIG. 1 ;

[0008] FIG. 3 is a simplified scheme illustrating the optional incorporation of the features described in FIG. 1 and FIG. 2 above with a lower gas-liquid contacting section operating with solvent intercooling; and

[0009] FIG. 4 is a simplified scheme illustrating yet another optional incorporation of the features of FIG. 1 with a lower gas-liquid contacting section operating with cooled solvent recirculation.DETAILED DESCRIPTION

[0010] The inventors hereof have discovered an efficient process and system for removing CO2 from a CO2-containing gas through absorption using an ammonia containing aqueous solvent. The system and process described herein can increase CO2 removal efficiency and / or decrease the required gas-liquid contacting device volume and / or reduce required steam consumption while simultaneously mitigating ammonia emission.

[0011] In the system and process described herein, a CO2-partially-enriched solvent is used to mitigate ammonia loss. Unlike a solvent with a higher CO2 loading, using a CO2- partially-enriched solvent for ammonia slip abatement allows the solvent to be cooled / chilled without the problems of precipitation and possible losses of CO2. Thus the process and system can achieve a significant reduction in ammonia slip while reducing negative impact on CO2 capture performance.

[0012] Moreover, the CO2-partially-enriched solvent with the recovered ammonia is returned to a height location in the absorber close to a height location from which it is drawn, which can minimize the disruption of the compositional driving forces and associated potential to capture CO2. The portion of relatively cool CO2-partially-enriched solvent with the recovered ammonia can also effectively cool the relatively warm CO2-partially-enriched solvent upon reintroduction and mixing in the absorber, which saves equipment, otherwise required for separate intercooling, by functional integration. In other words, the process and system can reduce ammonia emission by adding once through extraction of a CO2-partially- enriched solvent and return of the solvent after ammonia recovery while simultaneously acting as an effective method for solvent intercooling. In certain embodiments, the process and system can also minimize the associated absorber gas-liquid contacting device volume and avoid recirculation of solvent, which leads to further cost and energy savings.71CCS-510954- WO-2_BHI0566PCT

[0013] A detailed description of one or more embodiments of the disclosed process and system are presented herein by way of exemplification and not limitation with reference to the figure.

[0014] Referring to FIG. 1 to FIG. 4, absorber vessels (800, 900, and 1000) are provided. The absorber vessel (800, 900, 1000) is configured to receive a CO2-containing gas stream (A) via an inlet (15) located near the bottom of the vessel (800, 900, 1000) and to allow the CO2-containing gas stream (A) to flow upward and through the absorber vessel (800, 900, 1000) to exit via an outlet (85) located near the top of the vessel (800, 900, 1000) as a treated gas stream (B).

[0015] The CO2-containing gas stream (A) entering the absorber vessel (800, 900, 1000) can include air, natural gas, industrial effluents and commercial emissions. In an aspect, the CO2-containing gas stream is a flue gas stream, which can be the gas produced when fossil fuels such as coal, oil, natural gas, or wood are burned for heat or power.

[0016] The absorber vessel (800, 900, 1000) is configured to absorb CO2 in the CO2- containing gas stream (A), using an ammoniated aqueous solvent. As used herein, an ammoniated aqueous solvent refers to a solvent that contains ammonium ions and water. Optionally the ammoniated aqueous solvent also contains bicarbonate ions, carbonate ions, carbamate ions, potassium ions, dissolved alkanolamines (such as methyl-diethanolamine), or a combination comprising at least one of the foregoing contents.

[0017] Each absorber vessel (800, 900, 1000) includes, at least, a first absorber section (150), a second absorber section (250), and a third absorber section (350). When the absorber vessel is a column, the first, second, and third absorber sections (150, 250 and 350) can be located at the bottom, middle, and top sections of the absorber vessel (800) alternatively the absorber vessel (900, 1000) may also include additional sections (450) incorporated below the sections (150, 250, and 350) previously mentioned.

[0018] Each absorber section (150, 250, 350, 450) can include at least one gas-liquid contacting device (100, 200, 300, and 400), and a liquid distributor (105, 205, 305 and 405) configured to distribute a solvent into the gas-liquid contacting device. Absorber sections (150, 250, 350, 450) can further include dedicated liquid collectors (108, 208, 308 and 408) for collecting a solvent that has passed through the respective gas-liquid contacting device. The bottommost absorber section (150, 450) may optionally include a liquid collector (108, 408), to redirect liquid (such as indicated in 1000) but may otherwise not be required (such as for 800, 900).71CCS-510954- WO-2_BHI0566PCT

[0019] In each gas-liquid contacting device (150, 250, 350, 450), an ammoniated aqueous solvent contacts a CC -containing gas stream as the gas flows upwards through the absorber vessel (800, 900, 1000) and the ammoniated solvent travels downwards through the absorber vessel (800, 900, 1000). Gas-liquid contacting sections (150, 250, 350 and 450) can include, for example, structured or random packing materials.

[0020] Each liquid distributor (105, 205, 305 and 405) can be located at the top of the respective absorber section (150, 250, 350 and 450) and is configured to introduce an ammoniated aqueous solvent into the gas-liquid contacting devices (100, 200, 300 and 400). The liquid distributors may be configured as, for example, spray head nozzles, conduits with perforations, and / or slots, or a combination thereof.

[0021] The liquid collectors (108, 208, 308 and 408) may be arranged at the bottom of the respective absorber sections (150, 250, 350, and 450) to collect solvent having passed through the respective gas-liquid contacting devices (100, 200, 300 and 400). The liquid collectors (108, 208, 308 and 408) can also be configured to allow the CCh-containing gas stream rising up through the absorber vessel (800, 900, 1000) to pass through or alongside the liquid collectors. The liquid collectors may for example comprise a chimney tray. Other suitable known liquid collector designs can also be used. The liquid collectors can further have liquid outlets to remove the collected liquid. In some embodiments, the solvent which has passed through the gas-liquid contacting device (100) of the first absorber section (150) may be collected directly in a bottom portion of the absorber vessel (800, 900) such as a tank (50). In such embodiments, no liquid collector may be needed for the first absorber section (150, 450).

[0022] Each of the absorber sections (150, 250, and 350) carries out a particular phase of the CO2 absorption. In the process and system described herein, the second absorber section (250) is configured to capture CO2 in the CCh-containing gas stream at lower CO2 concentrations allowing a high level of overall CO2 capture efficiency. For example, the second absorber section (250) provides ample mass transfer driving force to efficiently capture the CO2 passing the first absorber section (150), allowing high overall capture efficiencies typically greater than 90% of the CO2 in the CO2-containing gas stream (A). Liquid exiting the second absorber has a CO2 concentration which is lower than the liquid exiting the first absorber section allowing this liquid to be cooled / chilled and recycled to the top of the third absorber section without precipitating dissolved species.

[0023] In the second absorber section (250) CCh-lean solvent (D) is introduced to the second liquid distributor (205) via liquid delivery path (25) and through a cooling device (28).71CCS-510954- WO-2_BHI0566PCTThe CCh-lean solvent (D) can be produced from a CO2 regenerator, and include water and ammonium ions, and optionally potassium ions, carbonate ions, bicarbonate ions, carbamate ions, potassium ions, dissolved alkanolamines (such as methyldiethanolamine), or a combination thereof. The CCh-lean solvent (D) from the regenerator is hot and needs to be cooled down before being introduced to the CO2 absorber (800, 900, 1000). Due to the composition of the CCh-lean solvent, CO2 has a tendency to go into and be dissolved in the solvent after moderate cooling. If the CCh-lean solvent is cooled down too much (or chilled to significantly below ambient temperature), slow liquid phase reactions helping otherwise to dissolve CO2 can hinder the uptake of said CO2, a moderate temperature may improve CO2 consuming reaction kinetics in the liquid phase and increase the overall rates of CO2 absorption or the rate of conversion of CO2 in vapor to dissolved CO2 in the form of ions such as carbamate, bicarbonate, and carbonate ions. The temperature of the CCh-lean solvent (D) is preferably high enough to avoid refrigeration, typically between 15 and 40 °C, more preferably between 20 and 30 °C, or about 25 °C, depending on ambient conditions and solvent composition.

[0024] Advantageously, in the process and system described herein, the CCh-lean solvent (D) is not mixed with any solvent from the third absorber section or the first absorber section. Rather, the CCh-lean solvent (D) passes through the gas-liquid contacting device (200) once without back-mixing with other solvents to maximize the CO2 absorption driving force. The configuration increases the potential for CO2 removal, and / or reduces absorber system packing volume.

[0025] The second liquid distributor (205) can distribute or spray a first portion of the CCh-lean solvent (D) into the second gas-liquid contacting device (200), where the CCh-lean solvent (D) contacts the CO2 gas stream rising through the contacting device (200) after entering from the first absorber section (150), which gas stream is also referred to as partially cleaned gas stream. During the contacting, CO2 in the partially clean gas stream dissolves further into the CCh-lean solvent (D) forming a CCh-partially-enriched solvent. The dissolution of CO2 forms carbamate, carbonate and / or bicarbonate ions. The dissolution reaction is exothermic, and heat generated from the reaction increases solvent temperature and may drive a portion of the ammonia dissolved in the CCh-lean solvent (D) into the gas phase. Accordingly, the gas stream exiting the second absorber section (250) after contacting CCh-lean solvent, contains reduced CO2 and increased ammonia concentrations (referred to as further cleaned gas stream containing ammonia). The further cleaned gas stream containing ammonia flows upwards from the second absorber section (250) to the third absorber section (350). After71CCS-510954- WO-2_BHI0566PCT capturing CO2 with a maximum possible concentration driving force, the CC -partially- enriched solvent is collected for redistribution. Since going through the contacting device (200) increases the solvent temperature, the collected CCL-partially-enriched solvent has a higher temperature than the CCL-lean solvent (D). The temperature of the CCT-parli ally-enriched solvent can have a temperature of about 25 to about 45 °C depending on ambient conditions and solvent composition.

[0026] The collected CCL-partially-enriched solvent is divided into a first portion (F) and a second portion (Z). The first portion (F) of the CCL-partially-enriched solvent is drawn from the second absorber section (250) using a pump (231), cooled / chilled by a cooling / chilling device (232 / 234), and then introduced into the third absorber section (350) to recover ammonia via a first liquid delivery path (230). Lowering the temperature of CCL-partially-enriched solvent (F) increases the ability of the solvent to absorb ammonia. In this way ammonia lost from the second absorber section (250) can be recovered, and ammonia slip can be mitigated. Ammonia quickly absorbs in aqueous solvents at low temperature, more quickly than CO2. Since the target of the third absorber section (350) is to absorb ammonia, liquid temperature can be lowered considerably without hindering ammonia mitigation. However, care must be taken to avoid lowering the temperature in the cooling / chilling device (232 / 234) to the point where precipitate may form in stream (230). The cooled / chilled CCL-partially-enriched solvent (F) entering the third absorber section (350) can have a temperature of about 5 to about 20 °C depending on solvent composition. Compared to extracting solvent from the bottom absorber section (150 or 450) for ammonia mitigation where the CO2 loading is the highest of all the absorber sections, extract solvent for ammonia slip abatement from second absorber section (250) allows the solvent to be cooled without problems of precipitation or potential losses of CO2. Accordingly, the process and system described herein reduces absorber ammonia slip and associated water wash requirements and stripper steam consumption of downstream processing equipment.

[0027] In an embodiment of absorber vessel (800) according to FIG. 1, stream (F) through liquid delivery path (235) can be divided after exiting the cooling device (232) with a portion proceeding through an additional chilling device (234) and then introduced into the top of the third absorber section (350) to recover ammonia. The optional second portion exiting the cooling device (232) can be introduced into the top of the second absorber section (250) via liquid delivery path (233).

[0028] Preferably the cooled CCh-partially-enriched solvent (F) is sprayed or introduced into the third gas-liquid contacting device (300) via the third liquid distributor (308),71CCS-510954- WO-2_BHI0566PCT where it contacts the further cleaned gas stream that contains ammonia generated from the second absorber section (250), producing a treated gas (B) and a solvent containing recovered ammonia (E). The treated gas (B) can exit the absorber vessel (800, 900, 1000) via an outlet (85).

[0029] The solvent with recovered ammonia (E) can be collected at the third liquid collector (308). Preferably the third absorber section (350) is configured such that solvent (E) does not flow into the second gas-liquid contacting device (200). In other words, the solvent (E) does not mix with the CCh-lean solvent (D). One advantage is that the CO2-lean solvent is not back-mixed with a solvent that is partially loaded with CO2 to avoid reduction of the CO2 capture driving force. Another advantage is that the lean solvent temperature is not lowered by mixing with the solvent used for recovering ammonia. Thus, in the process and system described herein the CO2-lean solvent fed to the absorber (800, 900, 1000) can maintain concentration driving force and maximize CO2 capture potential at optimal feed temperatures for the second absorber section (250).

[0030] The solvent (E) collected and drawn from the third absorber section (350) can flow down a second liquid delivery path (320) for delivery to the gas-liquid contacting device (100) in the first absorber section (150). The solvent (E) exiting the third absorber section (350) can have a temperature of about 10 to about 20 °C. It is important that the relatively cool solvent (E) is mixed with the second portion of the relatively warm CCh-partially-enriched solvent (Z) before passing into the first gas-liquid contacting device (100) in the first absorber section.

[0031] The second absorber section (250) typically has a height greater than 8 meters so that significant driving force is available to move the solvent containing the recovered ammonia (E) from the bottom of the third absorber section (350), for example the third liquid collector (308) to the top of the first absorber section (150), for example to the first liquid distribution device (105) or to the liquid collector (208) in the second absorber section (250) using gravity flow. The second absorber section (250) may also have multiple gas-liquid contacting sections.

[0032] The solvent containing the recovered ammonia (E) has a lower temperature than the second portion (Z) of the CCh-partially-enriched solvent. When the cool solvent containing the recovered ammonia (E) is mixed with the warm CCh-partially-enriched solvent (Z), the warm CCh-partially-enriched solvent (Z) is cooled, forming a mixed solvent (G) having a temperature that is lower than a temperature of the CCh-partially-enriched solvent (Z) thus achieving intercooling before the mixed solvent (G) is introduced into the first gas-liquid contacting device (100) in the absorber section (150). Accordingly, the CO2 capture system can71CCS-510954- WO-2_BHI0566PCT include a second liquid delivery path (320) for delivering a solvent (E) containing recovered ammonia drawn from the third absorber section to the second liquid collector (208) in the second absorber section (250) or to the first absorber section (150) at a height location that is above a first gas-liquid contacting device (100) in the first absorber section (150) so that the cool solvent containing the recovered ammonia and a second portion of the warm CO2- partially-enriched solvent are mixed above or in the first gas-liquid contacting device (100).

[0033] It is not critical how the mixing is conducted. The solvent (E) and solvent (Z) can be mixed in liquid collector (208) or in liquid distributor (105) before common distribution onto the first gas-liquid contacting device (100), or the solvent (E) and solvent (Z) can be distributed in parallel and allowed to mix above and in the first gas-liquid contacting device (100).

[0034] The process minimizes the disruption of the liquid potential to capture CO2, as the liquid removed (solvent F) is similar in composition to the liquid returned (solvent E). Meanwhile, the process reduces packing volume allowing faster liquid bulk reaction rates without compromise of increased ammonia slip.

[0035] The mixed solvent (G) enters the first absorber section (150) by way of the liquid distributor (105) of the first absorber section (150) using gravity flow. The function of the first absorber section (150) is to achieve the maximum loading of the solvent. In the first gas-liquid contacting device (100) of the first absorber section (150), the mixed solvent (G) contacts the CO2-containing gas stream (A), generating a partially cleaned gas stream and a CO2-enriched solvent (C). The partially cleaned gas stream flows upwards into the second absorber section (250). The CO2-enriched solvent (C) is collected at tank (50) before it is transferred out of the CO2 absorber (800) via an outlet (55) using a pump (56).

[0036] For high CO2 concentrations in the CO2-containing gas (A), the first absorber section (150) may be split in several sections to allow beneficial stagewise cooling of the liquid before capturing CO2 to maintain mass-transfer driving force. FIG. 3 and FIG. 4 provide two possible arrangements which accomplish stagewise cooling and bulk CO2 removal upstream the system provided in FIG. 1 and FIG. 2.

[0037] As indicated in FIG. 3 liquid (S) is collected by liquid collector (108) and provided to pump (131). The liquid is pumped by (131) over a cooler (132) back to the fourth absorption section (450) for distribution using liquid distributor (405) to the vapor liquid contactor (450). As option, to increase the CO2 content of the liquid flowing in conduit (F) for the purpose of improving ammonia removal in absorber section (350), a smaller portion of liquid from pump (131) can be provided to the suction of pump (231). The loaded solvent is71CCS-510954- WO-2_BHI0566PCT collected from the vapor liquid contactor (450) in the tower sump (50) and then transferred for solvent regeneration by pump (56). In this manner bulk CO2 removal can be executed upstream the system provided in FIG. 1.

[0038] As indicated in FIG. 4 liquid (S) is collected by liquid collector (108) and provided to a lower sump portion of the absorber where it is mixed with a portion of the liquid (Q) exiting the packing (450) to form a warm semi-rich solvent for recirculation. Pump (57) is used to recirculate liquid from the semi-rich sump over the cooler (58) before it is redistributed using liquid distributor (405) over the mass-transfer device (450). As option, to increase the CO2 content of the liquid flowing in conduit (F) for the purpose of improving ammonia removal in absorber section (350), a smaller portion of liquid from pump (57) can be provided to the suction of pump (231). Rich solvent exiting (450) is preferentially collected in the rich-solvent tank / sump (50) and a portion of which transferred for solvent regeneration by pump (56). A second portion of rich solvent (403) is transferred by overflow (Q) to the semi-rich tank / sump (51) where it mixes with the liquid portion (S) entering from the liquid collector (108).

[0039] The process and system described in FIG. 1, FIG. 2 provide means to avoid recirculation and back mixing from the lower most absorber section where the CO2 capture solvent has the highest liquid CO2 loading (below packing (150) in FIG. 1 and FIG. 2) to the top absorber section (350) where the partial pressure of CO2 in the vapor / gas phase is lowest. Reduced back-mixing increases the potential for CO2 removal and is of particular interest when processing flue gas with lower CO2 concentrations because it can reduce required absorber system packing volume and cost for a given CO2 removal target. In addition, the process and system allow for integrated ammonia slip abatement and solvent intercooling. Both features improve solvent CO2 loading and reduce associated steam consumption for solvent regeneration and downstream scrubbing of ammonia containing vapor / gas. With the disclosed process and system, ammonia slip reduction is improved by allowing colder recirculation temperatures not advantageous or possible when recirculating rich solvent due to possible solvent precipitation of salts, like ammonium bicarbonate.

[0040] Absorption of CO2 from the vapor / gas phase is exothermic which results in an increase in liquid solvent temperature. Tolerable increase in solvent temperature is limited by a “pinch condition” where mass transfer ceases due to increasing partial pressure of CO2 exerted by the solvent at increasing temperature to the point where it approaches the partial pressure of CO2 in the vapor / gas stream. For this reason additional contacting steps to cool solvent are required to moderate the increase of liquid solvent temperature when the concentration of CO2 in the vapor / gas stream (A) is high. FIG. 3 and FIG. 4 describe two71CCS-510954- WO-2_BHI0566PCT optional systems for providing cooling to an absorber section located below the configuration described in FIG. 1 and FIG. 2. Both systems include a fourth absorber section (450) located in the lower portion of the absorber (900, 1000) wherein the fourth absorber section, the first absorber section, the second absorber section, and the third absorber section are arranged sequentially in the absorber in a direction from the gas inlet to the gas outlet. Referring to FIG. 3 and FIG. 4, an absorber vessel (900, 1000) is provided having a fourth absorber section (450), which can include at least one gas-liquid contacting device (400), and a liquid distributor (405) configured to distribute a solvent into the gas-liquid contacting device. In these embodiments, the first absorber section (150) has a liquid collector (108).

[0041] Referring to the absorber (900) of FIG. 3, a substantial portion or preferably all of a CO2-semi-enriched solvent (S) collected at liquid collector (108) is drawn from the first absorber section (150) using a pump (131), the solvent (T) is sent to a cooling device (132) where it is cooled (U), and then the cooled CO2-semi-enriched solvent (U) is reintroduced to the top of the fourth absorber section (450) via a liquid delivery path (130) having liquid delivery paths (134, 135, 136) before or after the pump (131) and cooling device (132). Lowering the temperature of CO2-semi-enriched solvent (S, T) to (U) and reintroducing it back to the absorber close to a height location from which it is drawn maximizes absorption driving force between vapor and liquid through a reduction in liquid temperature. The cooled CO2- semi-enriched solvent (U) entering the fourth absorber section (450) can have a temperature of about 15 to about 40 °C, preferably about 20 to about 35 °C, or about 25 °C, depending on solvent composition.

[0042] Referring to the absorber (900) of FIG. 3, in an embodiment, a portion of the solvent (T) can be introduced into liquid delivery path (235) via liquid delivery path (617) to be combined with the CO2-partially-enriched solvent (F).

[0043] Referring to the absorber (900) of FIG. 3, the total liquid exiting the absorber as CO2-enriched solvent (P) is sent for regeneration.

[0044] Referring to the absorber (1000) of FIG. 4, all of a CO2-semi-enriched solvent (S) collected at liquid collector (108) is introduced to a CO2-semi-rich sump via a liquid delivery path (120) and allowed to mix with a portion of a CO2-enriched solvent (Q) drawn from a CO2-rich sump (50) via a liquid delivery path (403, baffle overflow). The C02-semi- rich sump (51) and CO2-rich sump (50) are separated by a baffle (59) or other separation means. The fourth absorber section (450) is provided with a means (613) to collect liquid and preferentially fill the rich sump (50) so as to allow an overflow of excess liquid to the semirich sump (51). A mixed CO2-semi-enriched solvent (W) is drawn from the CO2-semi-rich71CCS-510954- WO-2_BHI0566PCT sump, through liquid delivery path (614) using a pump (57); the mixed CCh-semi-enriched solvent (X) is sent via liquid delivery path (615) to a cooling device (58) where it is cooled (Y), and then introduced via liquid delivery path (616) to the top of the fourth absorber section (450). The cooled, mixed CCh-semi-enriched solvent (Y) entering the fourth absorber section (450) can have a temperature of about 20 to about 40 °C, preferably about 25 to about 35 °C, or about 30 °C, depending on solvent composition.

[0045] Further referring to the absorber (1000) of FIG. 4, all of the CCh-enriched solvent collected in the CCh-rich sump (50) which is not transferred to the semi-rich sump (51) exits the absorber via outlet (55) as a CCh-enriched solvent (R) to be sent for regeneration. Recirculation and back mixing as indicated in FIG. 4 is a means to moderate system temperature and extending the contact time between vapor and liquid; but is also associated with a reduction in mass transfer driving force.

[0046] Referring to the absorber (1000) of FIG. 4, in an embodiment, a portion of the solvent (X) can be introduced into liquid delivery path (235) via liquid delivery path (617) to be combined with the CO2-partially-enriched solvent (F).

[0047] Referring to the absorber (900, 1000) of FIG. 3 and FIG. 4, the absorber may further include a Periodic demister, Water Wash / Cleaning (370) located in the upper portion of the absorber, above the uppermost absorption section (350).

[0048] Set forth below are some systems and processes of the foregoing disclosure.

[0049] Aspect 1. A process of removing CO2 from a CO2-containing gas stream, the process comprising: contacting, in a first absorber section, a CO2-containing gas stream with a solvent mixture to generate a partially cleaned gas stream; contacting, in a second absorber section, the partially cleaned gas stream with a CO2-lean solvent to generate a further cleaned gas stream that contains ammonia and a CO2-partially-enriched solvent; dividing the CO2- partially-enriched solvent into a first portion and a second portion; removing the first portion of the CO2-partially-enriched solvent from the second absorber section; cooling the removed CO2-partially-enriched solvent; contacting, in a third absorber section, the cooled CO2- partially-enriched solvent with the further cleaned gas stream that contains ammonia to generate a treated gas stream and a solvent containing a recovered ammonia; and combining the solvent containing the recovered ammonia removed from the third absorber section with the second portion of the CO2-partially-enriched solvent, forming the solvent mixture used in the first absorber section; and one of A) or B): A) removing a CO2-semi-enriched solvent from a lower portion of the first absorber section and, after cooling, recirculating it to a fourth absorber section; or B) removing a CO2-semi-enriched solvent from a lower portion of the first71CCS-510954- WO-2_BHI0566PCT absorber section and circulating it to a CCh-semi-rich sump to mix with a portion of a CO2- enriched solvent, and removing a mixed CCh-semi-enriched solvent from the CCh-semi-rich sump and, after cooling, recirculating it to a fourth absorber section; wherein the fourth absorber section, the first absorber section, the second absorber section, and the third absorber section are arranged sequentially in an absorber in a direction from a gas inlet to a gas outlet.

[0050] Aspect 2. The process as in any prior Aspect, wherein the solvent with the recovered ammonia does not mix with the CCh-lean solvent.

[0051] Aspect 3. The process as in any prior Aspect, wherein the CCh-lean solvent introduced into the second absorber section is not mixed with any solvent obtained from the absorber section producing the CO2 enriched solvent or the third absorber section.

[0052] Aspect 4. The process as in any prior Aspect, wherein the CCh-lean solvent introduced into the second absorber section has a temperature of about 15 to about 35 °C.

[0053] Aspect 5. The process as in any prior Aspect, wherein the CCh-lean solvent introduced into the second absorber section comprises in part ammonium ions and water.

[0054] Aspect 6. The process as in any prior Aspect, wherein the solvent mixture is introduced into the first absorber section via gravity.

[0055] Aspect 7. The process as in any prior Aspect, wherein the cooled CCh-partially- enriched solvent has a temperature of about 5 to about 15 °C.

[0056] Aspect 8. The process as in any prior Aspect, wherein the solvent containing the recovered ammonia has a temperature of about 10 to about 20 °C.

[0057] Aspect 9. The process as in any prior Aspect, further comprising cooling the second portion of the CCh-partially-enriched solvent with the solvent containing the recovered ammonia.

[0058] Aspect 10. The process as in any prior Aspect, wherein the process does not include recirculation of a solvent from the absorber section producing the CO2 enriched solvent to the second absorber section.

[0059] Aspect 11. The process as in any prior Aspect, wherein the process does not include recirculation of a solvent from the absorber section producing the CO2 enriched solvent to the third absorber section.

[0060] Aspect 12. A CO2 capture system comprising an absorber vessel comprising a first absorber section, a second absorber section, and a third absorber section, the second absorber section comprising a second gas-liquid contacting device and a second liquid collector for collecting a CCh-partially-enriched solvent which is a lean solvent that has passed through the second gas-liquid contacting device; a gas inlet for introducing a CCh-containing gas stream71CCS-510954- WO-2_BHI0566PCT into the absorber vessel; a gas outlet for removing a treated gas stream from the absorber vessel; a liquid inlet for introducing the CCh-lean solvent into the second absorber section; a liquid outlet for removing a CCh-enriched solvent from the first absorber section; a first liquid delivery path for delivering an ammonia mitigation solvent, which is a first portion of the CO2- partially-enriched solvent collected on the second liquid collector, to the third absorber section; a cooling means for cooling the ammonia mitigation solvent before the ammonia mitigation solvent is delivered to the third absorber section; and a second liquid delivery path for delivering a solvent containing a recovered ammonia drawn from the third absorber section to the second liquid collector in the second absorber section so that the solvent with the recovered ammonia mixes with a second portion of the CCh-partially-enriched solvent; and one of A) or B): A) further comprising a fourth absorber section comprising a fourth gas-liquid contacting device and a fourth liquid distributor, and further comprising a liquid delivery path for delivering a CCh-semi-enriched solvent drawn from the first absorber section to the fourth liquid distributor; or B) further comprising a fourth absorber section comprising a fourth gasliquid contacting device and a fourth liquid distributor; further comprising a liquid delivery path for delivering a CCh-semi-enriched solvent collected at a first liquid collector of the first absorber section to a CCh-semi-rich sump to mix with a portion of a CCh-enriched solvent drawn from a CCh-rich sump; and a liquid delivery path for delivering a mixed CCh-semi- enriched solvent drawn from the CCh-semi-rich sump to the fourth liquid distributor; wherein the fourth absorber section, the first absorber section, the second absorber section, and the third absorber section are arranged sequentially in the absorber in a direction from the gas inlet to the gas outlet.

[0061] Aspect 13. The CO2 capture system as in any prior Aspect, wherein the third absorber section comprises a third liquid distributor, a third gas-liquid contacting device, and a third liquid collector, and the first liquid delivery path is configured to deliver the cooled ammonia mitigation solvent to the third liquid distributor.

[0062] Aspect 14. The CO2 capture system as in any prior Aspect, wherein the third liquid collector is configured such that the solvent with the recovered ammonia collected on the third liquid collector does not flow into the second absorber section to mix with the CCh- lean solvent.

[0063] Aspect 15. The CO2 capture system as in any prior Aspect, wherein the second liquid delivery path is configured to deliver the solvent containing the recovered ammonia collected at the third liquid collector of the third absorber section to the second liquid collector71CCS-510954- WO-2_BHI0566PCT in the second absorber section so that the solvent with the recovered ammonia mixes with a second portion of the CCh-partially-enriched solvent to form a mixed solvent.

[0064] Aspect 16. The CO2 capture system as in any prior Aspect, wherein the system is configured to deliver the mixed solvent to a liquid distributor of the third absorber section.

[0065] Aspect 17. The CO2 capture system as in any prior Aspect, wherein the second liquid distributor in the second absorber section is configured to receive the CCh-lean solvent and distributes the CCh-lean solvent into the second gas-liquid contacting device.

[0066] Aspect 18. The CO2 capture system as in any prior Aspect, wherein the system does not include a fluid delivery path to deliver a solvent from the absorber section producing the CO2 enriched solvent to the second absorber section.

[0067] Aspect 19. The CO2 capture system as in any prior Aspect, wherein the system does not include a fluid delivery path to deliver a solvent from the absorber section producing the CO2 enriched solvent to the third absorber section.

[0068] Aspect 20. The CO2 capture system as in any prior Aspect, wherein for A) the liquid delivery path for delivering the CCh-semi-enriched solvent drawn from the first absorber section comprises a means for controlling the temperature and flow of the CCh-semi-enriched solvent; and for B) the liquid delivery path for delivering the mixed CCh-semi-enriched solvent drawn from the CCh-semi-rich sump comprises a means for controlling the temperature and flow of the mixed CCh-semi-enriched solvent.

[0069] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. As used herein, “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like. All references are incorporated herein by reference.

[0070] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “about”, “substantially” and “generally” are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” and / or “substantially” and / or “generally” can include a range of ± 8% of a given value.

[0071] While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various71CCS-510954- WO-2_BHI0566PCT changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited.

Claims

71CCS-510954- WO-2_BHI0566PCTCLAIMS1. A process of removing CO2 from a CCh-containing gas stream, the process characterized by: contacting, in a first absorber section (150), a CCh-containing gas stream with a solvent mixture to generate a partially cleaned gas stream; contacting, in a second absorber section (250), the partially cleaned gas stream with a CCh-lean solvent to generate a further cleaned gas stream that contains ammonia and a CO2- partially-enriched solvent; dividing the CCh-partially-enriched solvent into a first portion and a second portion; removing the first portion of the CCh-partially-enriched solvent from the second absorber section (250); cooling the removed CCh-partially-enriched solvent; contacting, in a third absorber section (350), the cooled CCh-partially-enriched solvent with the further cleaned gas stream that contains ammonia to generate a treated gas stream and a solvent containing a recovered ammonia; and combining the solvent containing the recovered ammonia removed from the third absorber section (350) with the second portion of the CCh-partially-enriched solvent, forming the solvent mixture used in the first absorber section (150); and one of A) or B):A) removing a CCh-semi-enriched solvent from a lower portion of the first absorber section (150) and, after cooling, recirculating it to a fourth absorber section (450); orB) removing a CCh-semi-enriched solvent from a lower portion of the first absorber section (150) and circulating it to a CCh-semi-rich sump (51) to mix with a portion of a CO2- enriched solvent, and removing a mixed CCh-semi-enriched solvent from the CCh-semi-rich sump (51) and, after cooling, recirculating it to a fourth absorber section (450); wherein the fourth absorber section (450), the first absorber section (150), the second absorber section (250), and the third absorber section (350) are arranged sequentially in an absorber (900, 1000) in a direction from a gas inlet (15) to a gas outlet (85).

2. The process of claim 1 , wherein the solvent with the recovered ammonia does not mix with the CCh-lean solvent.

3. The process of claim 1, wherein the CCh-lean solvent introduced into the second absorber section is not mixed with any solvent obtained from the absorber section producing the CO2 enriched solvent or the third absorber section (350).

4. The process of claim 1 , wherein the CCh-lean solvent introduced into the second absorber section (250) has a temperature of about 15 to about 35 °C.71CCS-510954- WO-2_BHI0566PCT5. The process of claim 1, wherein the CC -lean solvent introduced into the second absorber section (250) comprises in part ammonium ions and water.

6. The process of claim 1, wherein the solvent mixture is introduced into the first absorber section (150) via gravity.

7. The process of claim 1, wherein the cooled CCh-partially-enriched solvent has a temperature of about 5 to about 15 °C.

8. The process of claim 1, wherein the solvent containing the recovered ammonia has a temperature of about 10 to about 20 °C.

9. The process of claim 1, further comprising cooling the second portion of the CCh-partially-enriched solvent with the solvent containing the recovered ammonia.

10. The process of claim 1, wherein the process does not include recirculation of a solvent from the absorber section producing the CO2 enriched solvent to the second absorber section (250).

11. The process of claim 1, wherein the process does not include recirculation of a solvent from the absorber section producing the CO2 enriched solvent to the third absorber section (350).

12. A CO2 capture system characterized by: an absorber vessel (900, 1000) comprising a first absorber section (150), a second absorber section (250), and a third absorber section (350), the second absorber section (250) comprising a second gas-liquid contacting device (200) and a second liquid collector (208) for collecting a CCh-partially-enriched solvent which is a lean solvent that has passed through the second gas -liquid contacting device (200); a gas inlet (15) for introducing a CCh-containing gas stream into the absorber vessel (900, 1000); a gas outlet (85) for removing a treated gas stream from the absorber vessel (900, 1000); a liquid inlet for introducing the CCh-lean solvent into the second absorber section (250); a liquid outlet for removing a CCh-enriched solvent from the first absorber section (150); a first liquid delivery path for delivering an ammonia mitigation solvent, which is a first portion of the CCh-partially-enriched solvent collected on the second liquid collector (208), to the third absorber section (350); a cooling means for cooling the ammonia mitigation solvent before the ammonia mitigation solvent is delivered to the third absorber section (350); and71CCS-510954- WO-2_BHI0566PCT a second liquid delivery path for delivering a solvent containing a recovered ammonia drawn from the third absorber section (350) to the second liquid collector (208) in the second absorber section (250) so that the solvent with the recovered ammonia mixes with a second portion of the C b-parli ally-enriched solvent; and one of A) or B):A) further comprising a fourth absorber section (450) comprising a fourth gas-liquid contacting device (400) and a fourth liquid distributor (405), and further comprising a liquid delivery path for delivering a CCh-semi-enriched solvent drawn from the first absorber section (150) to the fourth liquid distributor (405); orB) further comprising a fourth absorber section (450) comprising a fourth gas-liquid contacting device (400) and a fourth liquid distributor (405); further comprising a liquid delivery path for delivering a CCh-semi-enriched solvent collected at a first liquid collector (108) of the first absorber section (150) to a CCh-semi-rich sump (51) to mix with a portion of a CCh-enriched solvent drawn from a CCh-rich sump (50); and a liquid delivery path for delivering a mixed CCh-semi-enriched solvent drawn from the CCh-semi-rich sump (51) to the fourth liquid distributor (405); wherein the fourth absorber section (450), the first absorber section (150), the second absorber section (250), and the third absorber section (350) are arranged sequentially in the absorber in a direction from the gas inlet (15) to the gas outlet (85).

13. The CCh capture system of claim 12, wherein the third absorber section (350) comprises a third liquid distributor (305), a third gas-liquid contacting device (300), and a third liquid collector (308), and the first liquid delivery path is configured to deliver the cooled ammonia mitigation solvent to the third liquid distributor (305).

14. The CO2 capture system of claim 12, wherein the third liquid collector (308) is configured such that the solvent with the recovered ammonia collected on the third liquid collector (308) does not flow into the second absorber section (250) to mix with the CCh-lean solvent.

15. The CO2 capture system of claim 12, wherein the second liquid delivery path is configured to deliver the solvent containing the recovered ammonia collected at the third liquid collector (308) of the third absorber section (350) to the second liquid collector (208) in the second absorber section (250) so that the solvent with the recovered ammonia mixes with a second portion of the CCh-partially-enriched solvent to form a mixed solvent.

16. The CO2 capture system of claim 12, wherein the system is configured to deliver the mixed solvent to a liquid distributor (305) of the third absorber section (350).71CCS-510954- WO-2_BHI0566PCT17. The CO2 capture system of claim 12, wherein the second liquid distributor (205) in the second absorber section (250) is configured to receive the CC -lean solvent and distributes the CCh-lean solvent into the second gas-liquid contacting device (200).

18. The CO2 capture system of claim 12, wherein the system does not include a fluid delivery path to deliver a solvent from the absorber section producing the CO2 enriched solvent to the second absorber section (250).

19. The CO2 capture system of claim 12, wherein the system does not include a fluid delivery path to deliver a solvent from the absorber section producing the CO2 enriched solvent to the third absorber section (350).

20. The CO2 capture system of claim 12, wherein for A) the liquid delivery path for delivering the CCh-semi -enriched solvent drawn from the first absorber section (150) comprises a means for controlling the temperature and flow of the CCh-semi-enriched solvent; and for B) the liquid delivery path for delivering the mixed CCh-semi-enriched solvent drawn from the CC -semi-rich sump comprises a means for controlling the temperature and flow of the mixed CCh-semi-enriched solvent.

Images